Interim report of the Miners' Phthisis Prevention Committee = Tussentijds rapport van de Kommissie ter voorkoming van mijntering.

  • South Africa. Miners' Phthisis Prevention Committee.
Date:
1913
Catalogue details

Licence: In copyright

Credit: Interim report of the Miners' Phthisis Prevention Committee = Tussentijds rapport van de Kommissie ter voorkoming van mijntering. Source: Wellcome Collection.

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    that no precaution was taken to prevent the larger particles from getting into the filter tube. All the following determinations refer to fine dust only. In 1912, at the Jumpers Deep Mine, comparative experiments were made when dry drilling was being carried on, the sides of the drive being alsa dry, when an average of nine estimations showed 59 milligrams of fine dust. Another nine estimations, when drilling wet, and with the sides of the drive wet, gave 15 milligrams. Four other series of experiments (made chiefly at the City Deep Mine in 1912), where water was used, showed averages of from 4 milligrams to 8 milligrams of dust in the air. The Committee is quite satisfied that dust catchers are of little value in drilling; and that the only way to keep the atmosphere reasonably clear of floating dust is to prevent its formation by the abundant use of water delivered into the holes whilst being drilled. Immediately after blasting in a drive a sample taken 200: feet from the face gave 151 milligrams; and an experiment, where two sprays were installed, showed that the air contained 91 milligrams of dust after passing the sprays, in one hour after blasting the amount had become reduced to 8 milligrams, and in two hours to 2 milligrams. In another experiment, where a water-blast was used, two esti- mations, 30 minutes after blasting, gave 8 milligrams and 16 milligrams of dust in the air, respectively; one hour after blasting 6 milligrams were found. These experiments show that, although with the free use of water much the greater pro- portion of the dust is quickly laid, a certain amount remains in suspension in the „air for a longer period. (b) Stopes. The average amount of dust in stopes, whilst drilling was proceeding, varied from 4 to 6 milligrams. No measurements have yet been made with regard to the dust in stopes after blasting. (c) Shovelling. An experiment was made in an engine chamber, which was being cut under- ground, with a view to testing the effect of shovelling rock dry, as compared with shovelling it wet. When shovelling the rock dry, six measurements showed that there was an average of 18 milligrams of dust in the air; when shovelling the rock wet, three measurements each showed 2 milligrams of dust.’ It would seem, therefore, that the proper wetting of rock, before and during shovelling, is an efficient means of preventing the dissemination of dust by such operations, (d) Return Air-ways and U pcasts. Ae 14 An interesting series of experiments was made at the Aurora West Mine, where the current of air passes downwards through a series of stopes to the 10th level, which serves as a return air-way. Two measurements of the dust in the return air-way, in the morning, gave 1:3 milligrams and 1:2 milligrams. In the air-way a water-blast, two sprays, and a water-door—that is, a door with wire gauze thoroughly wetted—were placed to see what amount of thé dust made in blasting could be laid by these devices. Numerous measurements were made, of which the following may be considered typical.’ Before the air reached the devices, immediately after blasting, the dust, taken over a period of twenty-five minutes, proved to be 286 milligrams.* The air which passed the spraying devices, taken over three consecutive intervals of fifteen minutes each, contained 80 milligrams, 40 milligrams, and 36 milligrams of dust, respectively. Another series of experi- ments was made to see how quickly the dust abated after passing through the dust- laying devices. In the first five minutes, there were 164 milligrams of dust in the air, in the second five minutes 84 milligrams; and then in four consecutive inter- vals of fifteen minutes each, the following amounts were obtained: 24 milligrams, 17 milligrams, 11 milligrams and 13 milligrams. The results obtained in these experiments are instructive. In the first place, they show how large an amount of dust may he present in mine air after general blasting. It may be that the amount was larger than is usual in other mines, which might have been due, in part, to the fact that the current passed down- wards through the stopes. Secondly, the experiments show that water-blasts, sprays and other devices, are powerless to eliminate entirely the dust from the air * On two other occasions, under these circumstances, the dust was returned at 540 and 425 milligrams, -° respectively,